Foot prosthesis having cushioned ankle

ABSTRACT

A simple, inexpensive prosthetic foot is provided incorporating a cushioned ankle including an ankle block formed of a resilient material or bladder having desired compliance and energy return characteristics. The ankle block is sandwiched between a foot element and an ankle element. One or more openings extends through the ankle block with a substantially transverse orientation relative to a forward walking motion. The size and shape of these openings, as well as the insertion of different types of stiffeners therein, provide desired performance characteristics to the ankle block. When the ankle block takes the form of one or more inflatable bladders, the pressure within these bladders is individually controlled by valves to provide desired performance characteristics to different portions of the prosthetic foot. A pump system can also be used to control and generate fluid pressure into these bladders. A preferred pump system generates fluid pressure based upon the movement of the amputee onto two telescoping pylons that are connected to the prosthetic foot.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 09/698,489,filed Oct. 26, 2000 now U.S. Pat. No. 6,899,737, which is acontinuation-in-part of application Ser. No. 09/288,869, filed Apr. 9,1999, now U.S. Pat. No. 6,280,479, which is a continuation-in-part ofapplication Ser. No. 09/138,357, filed Aug. 21, 1998, now U.S. Pat. No.6,206,934, which claims the benefit of Provisional Application Ser. No.60/081,472, Apr. 10, 1998. This application is also acontinuation-in-part of application Ser. No. 09/957,971, filed Sep. 20,2001 now abandoned, which is a continuation of application Ser. No.09/452,032, filed Nov. 30, 1999, now abandoned, which is a continuationof application Ser. No. 09/078,450, filed May 13, 1998, now U.S. Pat.No. 5,993,488, which is a continuation of application Ser. No.08/515,557, filed Aug. 15, 1995, now U.S. Pat. No. 5,800,569, which is acontinuation-in-part of application Ser. No. 08/290,339, filed Aug. 15,1994, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to prosthetic feet and, more particularly,to a simply constructed, low-profile prosthetic foot having enhancedperformance characteristics.

2. Description of the Related Art

In the prosthetics market, the conventional SACH (solid-ankle,cushion-heel) foot has been the most widely prescribed artificial footover the past 35 years. The SACH foot generally includes a solid ankleand cushioned heel foot mounted to a limb along an approximate hingeaxis taken through the ankle. The SACH foot has been popular preciselyfor its simplicity, and thus economy, but includes certain drawbacks interms of dynamic response characteristics. Specifically, the low endSACH feet do not provide much energy storage and release, as do moresophisticated prosthetic feet.

Most modern foot prostheses incorporate some form of energy storageelement for storing and releasing walking energy. Conventionally, thismight consist of a spring-loaded ankle joint comprising metal coilsprings or, more commonly, rubber compliance members. Inexpensive footprostheses have also been devised having essentially a solid rubber orfoam ankle block for storing and releasing walking energy. Such an ankleblock has been disclosed in my issued patent titled PROSTHESIS WITHRESILIENT ANKLE BLOCK, U.S. Pat. No. 5,800,569, the entirety of which isincorporated by reference. A solid, compressible ankle block may besecured between upper and lower support members to provide resilientcompression and energy storage and release. The use of an ankle blockmember provides significant manufacturing and cost advantages. However,for certain applications it is difficult to attain a desired level ofspring compliance and energy return characteristics using a solid ankleblock due to the inherent limitations of the materials involved in termsof elasticity, viscosity and maximum compression.

SUMMARY OF THE INVENTION

One embodiment of the present invention provides a simple, inexpensiveprosthetic foot incorporating an ankle block having selectablecompliance and energy return characteristics that may be varied over awider range to accommodate the different weight, height and activitylevel of amputees. The ankle block is formed of compressible materialhaving desired compliance and energy return characteristics. The ankleblock is sandwiched between a foot element and an ankle element. One ormore spring inserts are embedded inside the ankle block to increase therigidity of the prosthetic foot and to improve the degree of energystorage and return. The shape of the spring inserts is preferably onethat supports compression during relative angular rotation of the ankleplate and foot plate elements, such as during toe and heel roll, andalso vertical compression, such as in response to vertical shock loads.

In one aspect of the present invention, a basic prosthetic foot isprovided having enhanced performance characteristics generallycomprising a lower foot plate, an upper ankle plate, a foam ankle blockjoining the two plates, and a spring element embedded in the ankleblock. Both the foot plate and the ankle plate are constructed ofstrong, flexible material, preferably a laminate of composite material.The foot plate is sized approximately equal to a human foot beingreplaced, while the ankle plate has a similar width, but has a shorterlength than the foot plate. The ankle block has a length and widthapproximately equal to the ankle plate and is aligned therewith. Thespring element comprises two relatively flat carbon fiber compositemembers secured at their middle and separated at their ends. This givesthe spring element a preferable shape of a bow tie or double wishbone.Preferably, an attachment member couples the ankle plate to a stump orlower-limb pylon of the wearer. During walking, the combination of theresilient ankle block with embedded spring element and flexible platesprovides a smooth rollover from a heel-strike to a toe-off position.

In another aspect, the ankle block of a prosthetic foot may be providedwith cylindrical openings both in the fore and aft positions of theankle block. These openings enable the placement of additional insertsor stiffeners to give the block a desired rigidity. In a preferredembodiment, the foot element also has a tapered thickness. Further, thefoot element comprises uplifted heel and toe ends and an arch regiontherebetween.

In another aspect, a prosthetic foot is provided comprising a foot plateelement, at least one ankle plate element and an ankle block sandwichedbetween the foot plate element and the ankle plate element. The footplate element has a length approximately equal to the length of a humanfoot, and comprises a resilient material capable of flexing along itslength. The at least one ankle plate element has a length substantiallyshorter than the foot plate element. The ankle block comprises arelatively soft, compressible material and provides substantially thesole means of support and connection between the foot plate element andthe ankle plate element. At least one opening extends through the ankleblock with a substantially transverse orientation relative to a forwardwalking motion. The foot plate element and the ankle block flex in acooperative manner to provide substantially smooth and continuousrollover transition from heel-strike to toe-off.

In another aspect, a prosthetic foot comprises a lower foot plate, anupper ankle plate disposed above and generally over the lower foot plateand being spaced therefrom, and a plurality of inflatable bladdersdisposed between the upper ankle plate and the lower foot plate andseparating the upper plate from the lower plate. The bladders providesubstantially the sole means of support between the foot plate and theankle plate. The foot plate and the bladder flex in a cooperative mannerto provide substantially smooth and continuous rollover transition fromheel-strike to toe-off.

In another aspect, a prosthetic foot for connecting to a pylon of anamputee is provided. The prosthetic foot comprises a foot plate elementhaving a length approximately equal to the length of a human foot, anankle plate having a length substantially shorter than the foot plateelement, and at least one inflatable bladder between the ankle plateelement and the foot plate element. The foot plate element comprises aresilient material capable of flexing along its length. The at least oneinflatable bladder provides substantially the sole means of support andconnection between the foot plate element and the ankle plate element. Afluid pump generates fluid pressure based on the movement of the amputeeonto the pylon. A fluid pathway directs fluid into the at least oneinflatable bladder.

In another aspect, a pump system for a prosthetic foot is provided. Thesystem comprises at least one inflatable bladder, a syringe including aplunger and a cylinder, a fluid pathway connecting the syringe to the atleast one inflatable bladder, and a first pylon and a second pylontelescopingly engaged. The plunger is connected to the first pylon andthe cylinder is connected to the second pylon, such that relativemovement between the first and second pylon moves the plunger in and outof the cylinder to generate pressure within the at least one inflatablebladder.

In another aspect, a prosthetic foot is provided comprising an innerpylon and an outer pylon that are telescopingly engaged. A compressiblemember is positioned in a chamber defined between the inner and outerpylons. The inner pylon moves relative to the outer pylon upon theapplication and release of a compressive force onto the prosthetic foot.A fluid line is also provided in communication with the chamber. Atleast one inflatable bladder is in communication with the fluid line,and fluid pressure is generated in the at least one inflatable bladderbased on the relative movement between the inner and outer pylons. Inanother aspect, a prosthetic foot comprises a foot plate elementcomprising a resilient material capable of flexing along its length, andat least one ankle plate element. An ankle block comprising a relativelysoft, compressible material is sandwiched between the ankle plateelement and the foot plate element. The ankle block providessubstantially the sole means of support and connection between the footplate element and the ankle plate element. At least one opening extendsthrough the ankle block with a substantially transverse orientationrelative to a forward walking motion. At least one cam is inserted intothe at least one opening, the cam being rotatable to locally adjust thestiffness of the ankle block.

In another aspect, the prosthetic foot having a foot plate element, atleast one ankle plate element and an ankle block sandwichedtherebetween, includes a first and second chamber extending through theankle block. The first chamber is positioned in a fore portion of theblock and the second chamber is positioned in a rear portion of theblock, the first and second chambers being oriented generally transverseto a forward walking motion. First and second stiffeners are positionedin the first and second chambers, respectively, the first and secondstiffeners being moveable within each of said chambers.

In another aspect, a prosthetic foot is provided comprising a foot plateelement comprising a resilient material capable of flexing along itslength, and at least one ankle plate element. An ankle block comprisinga relatively soft, compressible material is sandwiched between the ankleplate element and the foot plate element. The ankle block providessubstantially the sole means of support and connection between the footplate element and the ankle plate element. The ankle block includes awedge cut-out in a rear portion of the ankle block. In one embodiment,the prosthetic foot further comprises a wedge piece inserted into thewedge cut-out.

In another aspect, the prosthetic foot comprising a foot plate element,at least one ankle plate element and an ankle support member sandwichedtherebetween is further provided with a strap connecting the ankle plateelement to the foot plate element. The strap is positioned behind theankle block relative to a forward walking motion and is capable ofadjusting the relative flexing properties between said ankle plateelement and said foot plate element.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described herein above. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught herein without necessarilyachieving other objects or advantages as may be taught or suggestedherein.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments of the presentinvention will become readily apparent to those skilled in the art fromthe following detailed description of the preferred embodiments havingreference to the attached figures, the invention not being limited toany particular preferred embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prosthetic foot in one embodiment ofthe present invention.

FIG. 2 is a cross-sectional view of a prosthetic foot in one embodimentof the present invention.

FIG. 3 is a perspective view of a spring element embedded in the ankleblock in one embodiment of the present invention.

FIG. 4 is a side elevational view of a prosthetic foot more clearlyshowing a foot plate having a tapered thickness along its length.

FIG. 5A is a sectional view of a prosthetic foot in a heel-strikeposition of a walking stride.

FIG. 5B is a sectional view of a prosthetic foot in a flat position of awalking stride.

FIG. 5C is a sectional view of a prosthetic foot in a heel-off positionof a walking stride.

FIG. 5D is a sectional view of a prosthetic foot in a toe-off positionof a walking stride.

FIG. 6 is a cross-sectional view of an alternative embodiment of aprosthetic foot of the present invention incorporating a modified springelement.

FIG. 7 is a cross-sectional view of another alternative embodiment of aprosthetic foot of the present invention incorporating a modified ankleblock.

FIG. 8 is a cross-sectional view of another alternative embodiment of aprosthetic foot of the present invention incorporating a modified ankleblock.

FIG. 9 is a cross-sectional view of another alternative embodiment of aprosthetic foot of the present invention incorporating an inflatablebladder ankle block.

FIG. 10 is a cross-sectional view of another alternative embodiment of aprosthetic foot of the present invention incorporating a multipleinflatable bladder ankle block.

FIG. 11A is a partial cross-sectional view of another alternativeembodiment of a prosthetic foot of the present invention incorporatingcylindrical slots.

FIGS. 11B–11D are perspective views of stiffeners that may be insertedinto the cavities of the prosthetic foot of FIG. 1A.

FIG. 12 is a partial cross-sectional view of another alternativeembodiment of a prosthetic foot of the present invention incorporatingdual ankle plates and cylindrical slots.

FIG. 13 is a partial cross-sectional view of another alternativeembodiment of a prosthetic foot of the present invention incorporatingtoe and heel air bladders.

FIG. 14 is a perspective view of the heel and toe bladders of FIG. 13.

FIG. 15A is a perspective view of the components of another alternativeembodiment of a prosthetic foot of the present invention incorporating ashock pumping system.

FIG. 15B is a schematic view of the valve manifold of the prostheticfoot of FIG. 15A.

FIG. 16A is a perspective view of another alternative embodiment of aprosthetic foot of the present invention incorporating the components ofFIG. 15A.

FIG. 16B is a perspective view of one embodiment of a prosthetic footincorporating a CO2 cartridge.

FIGS. 17 and 18 are partial cross-sectional view of additionalalternative embodiments of a prosthetic foot of the present inventionincorporating chambered urethane.

FIG. 19 is a partial cross-sectional view of another alternativeembodiment of a prosthetic foot of the present invention incorporatingrotatable cams.

FIG. 20 is a partial cross-sectional view of another alternativeembodiment of a prosthetic foot of the present invention incorporatingan actuator and moveable stiffeners.

FIG. 21 is a partial cross-sectional view of another alternativeembodiment of a prosthetic foot of the present invention incorporatingan adjustable strap and an insertable heel wedge piece.

FIG. 22 is a partial cross-sectional view of the prosthetic foot of FIG.21, further illustrating a C-shaped insert for tightening the adjustablestrap.

FIG. 23 is a partial cross-sectional view of prosthetic foot having aninflatable bladder in fluid communication with an active shock module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIGS. 1 and 2, a first embodiment of a prosthetic foot10 of the present invention is shown in a perspective view and across-sectional side view, respectively. The prosthetic foot 10generally comprises a lower foot plate 12, an upper, smaller ankle plate14, an ankle layer or block 16 made of resilient material, connectingthe foot plate 12 to the ankle plate 14, and a spring element 18embedded within the ankle block 16. The foot plate 12 has a length andwidth roughly equal to the approximate length and width of theparticular wearer's amputated foot and sized to fit within an outer,flexible cosmesis 30, shown in phantom. The ankle plate 14 and theresilient ankle block 16 have approximately the same horizontalcross-sectional size. The ankle plate 14, ankle block 16, and springelement 18 are centered transversely with respect to and are generallypositioned over the back half of the foot plate 12. The ankle block 16is sandwiched between the foot plate 12 and the ankle plate 14 and ispreferably glued or bonded to both plates using polyurethane adhesive orother known securement technologies.

The spring element 18 is a resilient support member inserted within theresilient ankle block 16. As shown in FIG. 3, the spring element 18 ispreferably comprised of upper and lower plate-like members 22 and 24,each of which is relatively flat and has a substantially rectangularvertical projection. These members are secured at their center by afastener 26 and separated at ends 80 and 82. The upper member 22preferably has a curvilinear concave upward shape, while the lowermember 24 preferably has a curvilinear concave downward shape. Thisgives the spring element 18 a substantially double wishbone or bow tieshape.

As shown in FIG. 1, the spring element 18 is completely embedded withinthe ankle block 16 so as not to be visible from the outside. Referringto FIG. 2, the spring element 18 extends substantially longitudinallyacross the length of the ankle block 16, and has a width substantiallyequal to the width of ankle block 16. The fastener 26 may comprisebolts, a weld, or any other fastening means as would be known to thoseskilled in the art. In the preferred embodiment, the fastener 26 is astrap which is laminated around the center portion of the two members22, 24. A wedge member 28, preferably of a resilient elastomer, isplaced between the two plate members 22, 24 to protect the innersurfaces of the members and to provide additional support to the springelement 18. The wedge 28 acts to provide leverage between the two platemembers 22, 24, and enables adjustment of the flexing characteristics ofthe spring element 18, if desired. Alternatively, it may be bondedpermanently in place or formed integrally with one or both of the platemembers 22, 24, as desired. Although the spring element 18 has beendescribed as having a double wishbone or bow tie configuration, othershapes and sizes may be appropriate for providing support to the ankleblock 16. Furthermore, more than one spring element may be provided inthe ankle block to provide support and energy return to the prostheticfoot 10.

As can be seen in FIGS. 1 and 2, the prosthetic foot 10 furthercomprises a pylon member 32 which can be secured to the stump of theamputee (not shown) and extends relatively downward therefrom in agenerally vertical direction. The pylon member 32 in the preferredembodiment is of tubular construction having a substantially equalmoment of inertia in all directions to restrict bending in alldirections. The tubular member 32 is also preferably hollow so that itis relatively light in weight and utilizes less material which reducesthe cost of production. The pylon member 32 is dimensioned so as to beinterchangeable with a standard 30 mm pylon. Other configurations whichimpart rigidity, such as rectilinear cross sections having relativelylarger moments of inertia about one or both transverse axes can also beutilized to obtain the benefits discussed herein. A centerline 70through pylon 32, shown in FIG. 1, defines the downward direction of theapplication of force.

As shown in FIGS. 1 and 2, the ankle plate 14 is secured to the pylonmember 32 through a vertically oriented upper attachment member 34. Theupper attachment member 34 is attached to a curvilinear ankle section36, which is connected to the ankle plate 14. Preferably, these threepieces are monolithically formed with one another for optimum strengthand durability. The attachment member 34 has a rearward surface 38, asshown in FIG. 2, and a forward surface 40 substantially parallelthereto. The attachment member 34 is substantially rigid and capable ofsustaining torsional, impact and other loads impressed thereupon by theprosthesis. In addition, the inherent rigidity of attachment member 34prevents it from being distorted in any substantial way and causes theeffective transmission of the aforesaid loads imposed thereupon to asuitable ancillary prosthetic pylon 32.

With reference to FIG. 2, the attachment member 34 is in the preferredembodiment vertically oriented so that it may be secured to the pylonmember 32. A coupling device 42 is positioned at the lower end of thepylon member 32 which provides a flat surface upon which the verticalattachment member 34 can be secured. The coupling device 42 has oneattachment surface 44 which mates with the cylindrical outer surface ofthe pylon member 32 and a second substantially flat attachment surface46 which mates with the attachment member 34. In the preferredembodiment, attachment surface 44 is curved to mate with the outersurface of the tubular pylon member 32, and attachment surface 46 isflat to accommodate the forward surface 40 of the attachment member 34.

Desirably, the coupling device 42 is welded or bonded to the pylonmember 32 and has two holes (not shown) into which two bolts 48 can beinserted and secured. The attachment member 34 also has two holes (notshown) which align with the holes on the coupling device to place andsecure the two bolts 48 through the attachment member 34 and thecoupling device 42. Other methods of securing the pylon member to thefoot portion are contemplated, such as those disclosed in my priorissued U.S. Pat. No. 5,514,186, the entirety of which is incorporated byreference, as well as those utilizing integrally formed constructions.

As stated, the attachment member 34 monolithically formed with the ankleplate 14 is vertically aligned so that it extends relatively downwardfrom the coupling device 42 on the pylon member 32. As shown in FIG. 2,the thickness of the attachment member 34 along this vertical section isrelatively greater than the thickness of the ankle plate 14substantially horizontally aligned along the foot portion. Theattachment member 34 is also made relatively thicker to support thevertical load imposed on the prosthetic device as well as to restrictundue bending at this juncture. The entire upper vertically-alignedsection of attachment member 34 is preferably of substantially uniformthickness and width.

The tubular pylon member 32 is preferably removable from the prostheticdevice such that the pylon member can be replaced without replacing theremainder of the prosthetic device. This permits Applicant's inventionto be utilized in a broader range of applications. For instance, thetubular member of Applicant's invention can be cut and adapted for useby amputees having different stump lengths including growing amputees.The prosthetist merely needs to cut a standard tubular pylon to theappropriate length. Moreover, this eliminates the need to manufacture asa part of the prosthesis a long rigid leg section. Thus, fewer materialsare needed to manufacture the prosthesis of Applicant's inventionresulting in reduced manufacturing costs.

The preferred embodiment further comprises cylindrical slots or openings50, 51 in the fore and aft portions of the ankle block 16, respectively,as shown in FIG. 2, to accommodate insertion of stiffeners 52, 53. Thecylindrical openings 50, 51 are disposed horizontally in a directiongenerally transverse to a forward walking motion, and between upper andlower plate members 22 and 24. Stiffeners 52, 53 can be removably placedin these openings to provide additional support and rigidity to theprosthetic foot 10, and also to modify the spring characteristics of theprosthetic foot. For instance, additional energy storage and return canbe provided for a more active amputee by inserting stiffeners 52, 53into ankle block 16 having a higher spring constant. On the other hand,when more control is desired, stiffeners with a lower spring constantmay be inserted to produce an ankle block 16 with greater dampeningcharacteristics. Alternatively, the cylindrical openings 50, 51 mayremain empty, thereby making the compliance characteristics dependentsolely on the ankle block 16 and the spring element 18.

Preferred Materials and Fabrication

Both the foot plate 12 and the ankle plate 14 are preferably formed of aflexible material so that flexing of the plates tends to relieve extremeshear stresses applied to the interfaces between the ankle block 16 andthe plates 12, 14. Both the foot plate 12 and the ankle plate 14 arepreferably constructed of fiberglass which provides strength andflexibility. The preferred material for the ankle plate 14 and the footplate 12 is a vinyl ester based sheet molding compound, such as Quantum#QC-8800, available from Quantum Composites of Midland, Mich.Alternatively, the plates may be formed by a plurality of laminaembedded in an hardened flexible polymer. In other arrangements, theplates may be formed of other materials such as carbon fiber compositesas may be apparent to one skilled in the art. The desirable propertiesof the plates are that they are relatively resilient so as to withstandcracking upon application of repeated bending stresses yet havesufficient flexibility to enhance the performance characteristics feltby the wearer in conjunction with the properties of the resilient ankleblock. The pylon member 32 is preferably made of a stiff material suchas a laminate of fiber reinforced composite. Stiffness in the pylonmember 32 can also be provided by a stiffer and more dense material.

The ankle block 16 is sandwiched between the foot plate 12 and the ankleplate 14 as shown in FIGS. 1 and 2 and is preferably bonded to bothplates. The ankle block is preferably formed of urethane, rubber orother suitable material having desired compliance and energy returncharacteristics. A preferred material for the ankle block is expandedpolyurethane foam such as cellular Vulkolka□ Pur-Cell No. 15-50, with adensity of approximately 500 kg/m3 as available from Pleiger PlasticsCompany of Washington, Pa. Alternatively, the ankle block 16 may bemolded or fabricated from a wide variety of other resilient materials asdesired, such as natural or synthetic rubber, plastics, honeycombstructures or other materials. Cellular foam, however, provides a highlevel of compressibility with desirable visco-elastic springiness for amore natural feeling stride without the stiffness drawbacks and limitedcompression associated with solid elastomeric materials. Furthermore,the cellular nature of a foam block makes it lighter than solidelastomers. Foam densities between about 150 and 1500 kg/m3 may be usedto obtain the benefits of the invention taught herein.

The spring element 18 is preferably made from a highly resilientmaterial that is capable of supporting compression during relativeangular rotation of the upper and lower members 12 and 14, such asduring toe and heel roll, and also vertical compression such as inresponse to vertical shock loads. One preferred material is carbon fibercomposites such as woven fiber mats and chopped fiber in an epoxymatrix. However, other materials with similar strength and weightcharacteristics will be known to those skilled in the art and may beused with efficacy. For instance, other filament types may be used, suchas glass, Kevlar and nylon by way of example, to ensure lightweight andstructural and dynamic characteristics consistent with the needs of aparticular amputee. The wedge 28 may be fabricated from a wide varietyof resilient materials, including natural and synthetic rubber,elastomeric polyurethane, or the like.

The ankle block 16 containing spring element 18 may be fabricated byinjecting a polyurethane elastomer into a mold allowing it to cure. Thespring element 18 may be inserted into the mold prior to injection ofthe polyurethane so that during curing, the polyurethane bonds to thespring member. Cylindrical slots or openings 50, 51 for insertion ofstiffeners 52, 53 may be provided in ankle block 16 by insertingcylindrical plugs into the block prior to injection of polyurethane.Alternatively, openings may be provided in the block after curing simplyby cutting or drilling away portions of the ankle block.

The stiffeners provided in the openings are preferably tubes of foammaterial having a density chosen according to desired compliancecharacteristics. A preferable material is expanded polyurethane having afoam density between about 150 and 1500 kg/m3. More preferably, adensity of about 250 to 750 kg/m3 is preferred to provide adequateadjustment of the energy storage and return characteristics of the foot.

Preferred Dimensions

As illustrated in FIG. 4, the foot plate 12 is preferably of curvilinearshape. The thickness t of foot plate 12 is preferably tapered along itslength, and the tapered profile corresponds approximately to the weightof the amputee. That is, for a heavier amputee, the thicknesses alongthe length would be greater than for a lighter weight amputee.Generally, the weight groups may be classified as light, medium, orheavy.

Table I below presents preferred groupings, as module sizes C/D/E, ofcosmesis sizes corresponding to a male “A” width shoe last. The sizesare presented by length L, width B at the forefoot and width H at theheel of the cosmesis.

TABLE I Cosmesis Sizes for Male “A” Width Shoe Last LENGTH L WIDTH BWIDTH H MODULE (cm) (cm) (cm) C 22 2.88 2.19 23 3.00 2.25 24 3.12 2.31 D25 3.25 2.44 26 3.38 2.50 27 3.50 2.56 E 28 3.62 2.69 29 3.75 2.75 303.88 2.81

Table II below presents preferred module sizes for various weight groupsof amputees.

TABLE II Modules vs. Weight Groups WEIGHT GROUP MODULE LIGHT MEDIUMHEAVY C CL CM — D DL DM DH E — EM EH

Table III below presents preferred taper thicknesses (t) for an averageor “DM” size foot plate 12, taken at positions spaced by distance x=0.1inch (2.54 cm).

TABLE III Taper Thickness t for DM Foot Plate POSITION THICKNESS t (x =2.54 cm) (cm) a 0.16 b 0.16 c 0.32 d 0.52 e 0.69 f 0.78 g 0.71 h 0.60 i0.48 j 0.28

The foot plate 12 has a heel end 54, toward the left in FIG. 4, which isconcave-upward or slightly uplifted from a horizontal plane P1tangential to the heel end 54 of the foot plate 12. Similarly, a toe end56, to the right of FIG. 4, is concave upward or somewhat uplifted froma horizontal plane P2 tangential to the front portion of the foot plate12. An arch section 58 is formed between the heel and toe ends and ispreferably concave-downward, as shown.

It is understood that within the cosmesis 30 (not shown), the tangentplane P1 of the heel end 54 is slightly raised a distance y relative tothe tangent plane P2 of the toe end 56, as shown. The DM-sized footplate of Table III, for example, has y=0.5 inches (1.27 cm). The footplate 12 is preferably 0.25 inches (0.63 cm) from the bottom or sole ofthe cosmesis 30. The cosmesis 30 may be insert molded using ananatomically sculpted foot shape, with details and sizing based on amaster pattern and/or digitized data representing typical foot sizes.

An intermediate region 58 comprising the arch portion of the foot plate12 has the greatest thickness of the foot plate 12. The curvature of thearch region 58 is defined by the cosmesis or shoe sole profile, andgenerally corresponds to selected ranges of human foot lengths.

The foot plate 12 of prosthesis 10 preferably has a length between about5 and 15 inches (about 13 and 38 cm), more preferably between about 8and 12 inches (about 20 and 30 cm) for the foot sizes given in Table I.The width of foot plate 12 is preferably about 1 to 4 inches (about 2.5to 8 cm). For the example given in Table III for a DM-sized foot plate12, the length of the plate 12 is approximately 9 inches (about 23 cm)and its width is about 2 inches (about 5 cm). The foot plate 12 has athickness between about 0.05 and 0.4 inches (about 0.1 and 1 cm), whichmore preferably may be tapered as indicated in Table III.

The ankle plate 14 of prosthesis 10 is substantially planar, and ispreferably shorter in length than the foot plate 12 and has a thicknessalso defined by the weight group of the wearer. The thickness of theankle plate is preferably about 0.05 to 0.4 inches (0.1 to 1 cm). Morepreferably, the corresponding ankle plate 14 in the present example isabout 0.2 inches (about 0.5 cm) thick at rear portion 62, tapering to athickness of about 0.1 inches (about 0.25 cm) at front portion 60. Theankle plate 14 preferably has a length of about 3 to 7 inches (about 8to 18 cm) and a width of about 1 to 3 inches (about 2.5 to 8 cm), morepreferably having length-width dimension of approximately 5×2 inches(about 13×5 cm). The ankle plate 14 is positioned at an angle such thatits front tip 60 is located closer to the foot plate 12 than its reartip 68. Relative to plane P3 shown in FIG. 4, the rear tip is preferablyraised an angle γ of about 5 to 30 degrees, and more preferably, about10 degrees.

The ankle block 16 is generally sized such that its upper surface isplanar and corresponds to the length and width of the ankle plate 14.The lower surface of the ankle block 16 is substantially curvilinear tomate with the curvilinear surface of foot plate 12. In the presentexample, the block 16 has a preferred thickness, at its front 66, ofabout 1 to 3 inches (about 2.5 to 8 cm), more preferably about 1.3inches (about 3.4 cm). Its thickness tapers to a minimum of about 0.5 to1 inch (about 1 to 2.54 cm), more preferably about 0.8 inches (about 2cm) adjacent arch portion 58. The rear 64 of the block 16 is preferablyabout 1 to 4 inches (about 2.5 to 10 cm) thick, more preferably about2.6 inches (about 6.6 cm) thick, which is about twice the thickness ofthe front portion 66 of the block 16. This gives the ankle block asubstantially wedge shape. The greater thickness at the rear of block 16is provided to impart additional support in the rear portion 64 of theankle block due to greater compressive forces on the rear of the footprosthesis caused by off-axis application of force relative to axis 70during heel strike (see FIG. 5A).

The ankle block 16 may be provided in varying heights or thicknesses, asdesired, but is most effective with a thickness of between about 1 and 4inches (about 2.54 and 10 cm). The front portion and rear surfaces ofankle block 16 are preferably angled according to the angle γ defined bythe plane P3 and the ankle plate 14. In other words, the ankle block hasfront and rear surfaces which are preferably sloped forward at an angleγ from vertical. The ankle block thus provides a relatively stiff, yetflexible ankle region which can be customized for various wearers.Heavier wearers may require a denser resilient material for the ankleblock, while lighter wearers may require a less dense material or lessthickness.

As shown in FIGS. 2 and 3, the spring element 18 is positioned in theankle block such that the center of the spring element 18, at theposition of fastener 26, is located approximately above the arch portion58 of foot plate 12. The two members 22, 24 of the spring element 18preferably have a constant thickness of about 0.05 to 0.2 inches (about0.1 to 0.5 cm). The distance between the two members at front end 82,when no load is impressed onto the foot 10, is preferably about 0.5 and2 inches (about 1 to 5 cm), more preferably about 0.7 inches (about 1.8cm). At rear end 80, when no load is impressed on the foot 10, thedistance between members 22 and 24 is about 1 to 3 inches (about 2.5 to7.5 cm), more preferably about 1.4 inches (about 3.5 cm). As describedin further detail below, when the foot is in a heel-strike position, therear end 80 of the spring element is compressed. When the foot is in atoe-off position, the forward end 82 of the spring element iscompressed.

The lengths, widths and thicknesses of the foot plate 12, ankle plate14, ankle block 16 and spring element 18 may be customized for thewearer according to his/her foot size as well as the approximate weightgroup of the wearer. Likewise, the material choice, and size for theseelements may be varied according to the wearer's foot size and weight.

The cylindrical openings 50, 51 provided in the fore and aft portions ofankle block 16 preferably have a diameter of about 0.1 to 0.4 inches(about 0.25 to 1 cm), and more preferably, about 0.2 inches (about 0.5cm). While the openings 50 and 51 shown in FIG. 2 have the samediameter, the diameters of the openings may be different to accommodatedifferent sized stiffeners. For instance, the diameter of opening 51 maybe made larger than the diameter of opening 50 to correspond with thegreater volume of ankle block 16 in rear portion 64.

Performance Characteristics

To more fully explain the improved performance characteristics of thepresent prosthetic foot 10, FIGS. 5A–5D show “snapshots” of a prostheticfoot in several positions of a walking stride. More particularly, FIG.5A shows a heel-strike position, FIG. 5B shows a generally flat ormid-stance position, FIG. 5C shows a heel-off position, and FIG. 5Dshows a toe-off position. Throughout the various positions shown for awalking stride, the present prosthetic foot 10 provides a smooth andgenerally life-like response to the wearer. During a walking stride, theankle block 16 transmits the forces imparted thereon by the foot plate12 and ankle plate 14, and experiences a gradual rollover, or migrationof the compressed region, from rear to front.

With specific reference to FIG. 5A, a first position of a walking stridegenerally entails a heel strike, wherein the wearer transfers all of hisor her weight to the heel of the leading foot. In this case, a rearportion 54 of the foot plate 12 comes in contact with a ground surface68, albeit through the cosmesis 30. The flexible nature of the footplate 12 allows it to bend slightly in the rear portion 54, but most ofthe compressive stresses from the weight of the wearer through theprosthetic foot 10 to the foot plate 12 are absorbed by a rear region 64of the ankle block 16 with spring element 18. The spring element 18 inthe rear portion contracts, such that the distance between members 22and 24 at rear end 80 decreases. In a front region 66 of the ankle block16, the spring element 18 may expand slightly such that the distancebetween members 22 and 24 at front end 82 increases. Front portion 66 ofthe ankle block 16 experiences a stretching, or tension, due to theattachment along the entire lower edge of the ankle block with the footplate 12, while rear portion 64 experiences compression. The contractionof the spring element 18 at end 80 and ankle block 16 at end 64 allowsthe prosthesis 10 to absorb and store energy from the compressivestresses during heel strike. Further, a slight amount of bending mayoccur in a rear region 68 of the ankle plate 14. The rear stiffener 53between members 22 and 24 is compressed so as to provide necessarysupport to the foot prosthesis and to prevent separation of the members22, 24 from the wedge 28. Front stiffener 52 is slightly stretchedsubstantially vertically due to the tension forces at front portion 66of ankle block 16.

Next, in FIG. 5B, the wearer reaches a generally flat-footed ormid-stance position, whereby the foot plate 12 contacts the ground 68along substantially its entire length, again through the cosmesis 30. Inthis position the weight of the wearer is directed substantiallydownwardly, so that the compression along the length of the ankle block16 is only slightly greater in the rear portion 64 than in front portion66, due to the off-center application of force. In both the fore andrear ends of spring element 18, the members 22 and 24 are compressedtowards each other, with the rear end 80 being slightly more compressedfrom its original position than the forward end 82. Likewise, stiffeners52 and 53 are compressed due to the downward application of force.Although this view freezes the compressive stress distribution as such,in reality the weight of the wearer is continually shifting from behindthe centerline 70 of the attachment member 34 to forward thereof. Thus,as the wearer continues through the stride, the compression of the ankleblock 16 and the elements embedded within travels from the rear portion64 toward the front portion 66. This migration of the compressed regioncan be termed “rollover.”

In a next snapshot of the walking stride, FIG. 5C shows the prostheticfoot 10 in a “heel-off” position. This is the instant when the wearer ispushing off using ball 72 and toe 74 regions of the foot. Thus, a largecompressive force is generated in the front region 66 of the ankle block16, causing the rear region 64 to experience a large amount ofseparation or tension. Similarly, the spring element 18 at the rear end80 expands between the two members 22, 24, while it compresses in thefront end 82. The front tip 56 of the foot plate 12 may bendsubstantially to absorb some of the compressive stresses. Likewise, thefront tip 60 of the ankle plate 14 may bend somewhat at this point. Itis important to note that although the ankle block 16 absorbs a majorityof the compression generated by the wearer, the foot plate 12 and ankleplate 14 are designed to work in conjunction with the resilient ankleblock and spring element and provide enhanced dynamic performance.Further, the flexing of the foot plate 12 and ankle plate 14 relievessome of the extreme shear stresses applied to the interfaces between theankle block 16 and plates, thus increasing the life of the bonds formedtherebetween. The stiffener 52 located in the front 66 of the ankleblock 16 compresses so as to limit compression of front end 82, givingthe wearer balance and to prevent separation of the members 22, 24 fromthe wedge 28. Stiffener 53 extends due to the separation of ankle block16 in rear portion 64.

In FIG. 5D, a final position of the walking stride is shown, wherein theprosthetic foot 10 remains in contact with the ground 68, but some ofthe weight of the wearer is being transferred to the opposite foot,which has now moved forward. In this “toe-off” position, there is lessbending of the front tip 56 of the foot plate 12 and less compression ofthe front portion 66 of the ankle block 16 and front end 82 of springelement 18. Likewise, the front tip 60 of the ankle plate 14 may flex aslight amount, depending on the material and thickness utilized. Theregion of highest compression of the ankle block 16 remains at thefarthest forward region 66, but it is reduced from the compression levelof the heel-off position of FIG. 5C. Thus, the rear portion 64 of theankle block 16 experiences a small amount of tension or spreading.

It can now be appreciated that the “feel” of the present prosthetic footis greatly enhanced by the cooperation between the foot plate, ankleplate, ankle block and spring inserts. As the wearer continues throughthe walking stride the dynamic response from the prosthetic foot issmooth as the ankle block with spring inserts compresses in differentregions. Further, the flexing of the ankle and foot plates assist insmoothly transmitting the various bumps and jars found in uneven walkingsurfaces.

Alternative Embodiments

It will be appreciated that many alternative embodiments of a prostheticfoot having features and advantages in accordance with the presentinvention may also be constructed and used with efficacy. One suchalternative embodiment is shown in FIG. 6. Reference numerals for FIG. 6generally correspond to the reference numerals used in FIGS. 1–5D forlike elements. Thus, the prosthetic foot 10 shown in FIG. 6 generallycomprises a lower foot plate 12, an upper, smaller ankle plate 14, anankle layer or block 16 made of resilient material, connecting the footplate 12 to the ankle plate 14, and a spring element 18 embedded withinthe ankle block. The foot plate 12 has a length and width roughly equalto the approximate length and width of the particular wearer's amputatedfoot and sized to fit within an outer, flexible cosmesis 30, shown inphantom. As shown in FIG. 6, the ankle plate 14 has a substantiallyarcuate curvature extending from the integrally formed attachment member34 to the front of the ankle plate 14.

More particularly, the spring element 18 as illustrated in FIG. 6 is aresilient support member inserted within the resilient ankle block 16.The spring element 18 shown in FIG. 6 is preferably a plate-like memberwith a curvilinear concave downward shape and a substantiallyrectangular vertical projection. The spring element 18 is preferablymade from a carbon fiber composite material such as describedhereinbefore, although other similar materials may be used as well.

FIG. 7 illustrates another alternative embodiment of the invention.Again, like reference numerals are generally used to indicate likeelements. Thus, the prosthetic foot 10 shown in FIG. 7 generallycomprises a lower foot plate 12, an upper, smaller ankle plate 14, andan ankle layer or block 16 made of resilient material, such as solid orfoam rubber or polyurethane, and connecting the foot plate 12 to theankle plate 14. The foot plate 12 has a length and width roughly equalto the approximate length and width of the particular wearer's amputatedfoot and sized to fit within an outer, flexible cosmesis 30, shown inphantom. As shown in FIG. 7, the ankle plate 14 transitions into asubstantially arcuate or curved ankle section 36 which is preferablyintegrally formed between the attachment member 34 and the ankle plate14.

FIG. 8 illustrates yet another alternative embodiment of the invention.Again, like reference numerals are generally used to indicate likeelements. Thus, the prosthetic foot 10 shown in FIG. 8 generallycomprises a lower foot plate 12, an upper, smaller ankle plate 14, andone or more ankle blocks 16 a, 16 b made of resilient material, such assolid or foam rubber or polyurethane, and connecting the foot plate 12to the ankle plate 14. If desired, the posterior ankle block 16 a mayhave a density or compliance characteristic which is different than thatof the anterior ankle block 16 b, so as to render it more soft and morecompliant, for example, than the anterior ankle block 16 b. Forinstance, this configuration could provide a more compliant heelresponse during heel strike.

Ankle blocks 16 a, 16 b may be formed integrally or separately, asdesired or as expedient. Preferably, they are positioned closelyadjacent to one another so as to occupy substantially the entire spacebetween the foot plate 12 and the ankle plate 14. The foot plate 12preferably has a length and width roughly equal to the approximatelength and width of the particular wearer's amputated foot and sized tofit within an outer, flexible cosmesis 30, shown in phantom. As shown inFIG. 8, the ankle plate 14 transitions into a substantially arcuate orcurved ankle section 36 which is preferably integrally formed betweenthe attachment member 34 and the ankle plate 14.

FIGS. 9 and 10 illustrate two other possible alternative embodiments ofthe invention. Again, like reference numerals are generally used toindicate like elements. Thus, the prosthetic foot 10 shown in FIG. 9generally comprises a lower foot plate 12, an upper, smaller ankle plate14, and, in this case, an inflatable bladder 19 disposed between thefoot plate 12 and the ankle plate 14. The bladder 19 has the furtheradvantage in that it enables the patient or prosthetist to vary theperformance characteristics of the prosthesis by adjusting the pressurein the bladder 19. This may be accomplished, for example, through theprovision of a valve means 21, which is provided in communication withthe bladder 19. In a preferred embodiment, the valve 21 is adapted toreceive a needle from an air pump (not shown) or from a CO2 cartridge(described with respect to FIG. 16B below), and may be suitably disposedon bracket 27, as illustrated in FIGS. 9 and 10. The valve 21 may beoperatively connected to bladder 19 via tubing or other suitablecommunication passage.

The bladder 19 may be secured via adhesive or other suitable affixingmeans to the upper ankle plate 14 and the lower foot plate 12 so as toprovide substantially the sole means of connection and supporttherebetween. Optionally, one or more retaining straps 23 may be used toprovide primary or secondary connection support, as needed or desired.Strap 23 may be fabricated from any number of suitably tough, flexiblematerials such as epoxy-impregnated canvas or the like. For example,straps 23 may be operatively attached to the forefoot portion of theprosthetic foot 10 as illustrated in FIG. 9 via adhesive, or nuts andbolts, or may be releasably attached around the structural member 12, 14through the provision of Velcro□-type fasteners or similar expedient.

The straps 23 provide a number of benefits. For example, if juxtaposedto a bladder member 19, the strap may be appropriately tightened to‘flatten’ the bladder, thus increasing the contact area between thestructural members 12, 14 and the bladder. Moreover, restraining meanssuch as the straps 23 may be incorporated to restrict the distance thatthe associated structural members 12, 14 may move from one another. Thestraps 23 may also be utilized to prevent undesirable excessive loadingand stressing of the structural members 12, 14 and/or the bladder 19.

The bladder 19 is preferably fabricated from a suitably strong,flexible, leak-proof, lightweight material such as urethane or the like.By way of example, the bladder may be formed by heat sealingappropriately sized and shaped pieces of urethane sheet to each other.Suitable thicknesses of urethane sheet material have been found to be0.01 to 0.02 inches (0.25–0.50 mm), but a wide range of suitablethicknesses and materials may also be utilized with efficacy. Bladderpressures of up to 80 psi (5.5 bar) have been utilized with efficacy.

The bladder 19 is preferably enwrapped in a covering material of Kevlaror similarly strong material to prevent the bladder 19 from explodingunder high pressures and to help define the final inflated shape of thebladder. In preferred embodiments, a covering may include top and bottomsections which are stitched together at the perimeter 25 of the bladder19. Those skilled in the art will understand that a variety of coveringmaterials and methods of fabrication and assembly thereof may be alsoutilized with efficacy, without departing from the teachings of theinvention.

Bladder 19 may enclose air, CO2, or a similar gas-like substance, or mayalternatively enclose liquids or gels such as water, silicone, or thelike. Any such assembly is preferably selected and adjusted to providethe desired deformability and consequent ‘cushioning’ effect orenergy-storing, absorption and release.

The bladder 19 may comprise a single chamber bladder, as illustrated inFIG. 9, or, optionally, it may comprise a multiple chamber bladders withor without venting provided between adjacent chambers. For example, thebladder could be bifurcated into anterior and posterior chambers orportions 19 a, 19 b such that the posterior portion 19 a can be adjustedto have a compliance characteristic which is different than that of theanterior portion 19 b, so as to render it more soft and more compliant,for example, than the anterior portion. This may be desirable, forinstance, to provide a more compliant heel response during heel strike.If desired or expedient, the bladder 19 may be tapered in shape so as topermit operative and proper alignment of the bladder between the ankleplate 14 and the foot plate 12.

Optionally, a spring element identical or similar to that illustratedand described above in connection with FIGS. 2–5, may be providedsubstantially completely within the bladder 19 (FIG. 9) so as to provideprimary or supplemental support between the foot and ankle plates, asdesired. For, example, the spring element may comprise two relativelyflat carbon fiber composite members secured at their middle andseparated at their ends. This gives the spring element a preferableshape of a bow tie or double wishbone. During walking, the combinationof the resilient spring element and inflatable bladder provides a smoothand adjustable rollover characteristic from a heel-strike to a toe-off,as desired.

The foot plate 12 preferably has a length and width roughly equal to theapproximate length and width of the particular wearer's amputated footand sized to fit within an outer, flexible cosmesis 30, shown inphantom. As shown in FIGS. 9 and 10, the ankle plate 14 transitions intoa substantially arcuate or curved ankle section 36 which is preferablyintegrally formed between the attachment member 34 and the ankle plate14.

FIG. 11A illustrates another prosthetic foot 10 similar to thatdescribed in FIGS. 1–4 above, but with several modifications asdescribed below. Accordingly, the prosthetic foot 10 of FIG. 11Agenerally comprises a lower foot plate 12, an upper, smaller ankle plate14, an ankle layer or block 16 made of resilient material, connectingthe foot plate 12 to the ankle plate 14, and cylindrical slots orcavities 50 and 51 allowing for the insertion of optional stiffeners 52and 53 (see FIGS. 11B–11D). The foot plate 12 has a length and widthroughly equal to the approximate length and width of the particularwearer's amputated foot and sized to fit within an outer, flexiblecosmesis 30, shown in phantom. As shown in FIG. 1A, the ankle plate 14has a substantially arcuate curvature extending from the integrallyformed attachment member 34 to the front of the ankle plate 14.

The ankle block 16 of FIG. 11A preferably has a front surface that issloped from the front edge of the ankle plate 14 forward to the footplate 12 there below. Similarly, the rear surface of the ankle block 16is preferably also sloped in a forward direction from the rear of theankle plate 14 in a forward direction to the foot plate 12. A strap 23such as described above is provided around the ankle plate 14, ankleblock 16 and foot plate 12, preferably over a rear portion of theprosthetic foot.

FIGS. 11B–11D show three examples of stiffeners that can be insertedinto the cavities 50 or 51. FIG. 11B illustrates a stiffener 52 (or 53)that is substantially cylindrical in shape and is comprisedsubstantially entirely out of foam. FIG. 11C shows a similar cylindricalstiffener 52, having a cylindrical opening 96 extending therethrough andopen on each end such that the stiffener is hollow and has asubstantially tubular configuration. The size of the opening 96 can bevaried to achieve a desired degree of compliance for the stiffener 52.FIG. 11D illustrates a stiffener 52 defining a cylindrical cavity 96therein being closed at each ends. A tube 98 is connected to the cavity96 such that air or another gas or fluid can flow into and out of theopening to provide a desired pressure within the opening to control thedegree of compliance of the stiffener. Thus, the opening 96 serves as aninflatable bladder. One or more valves (not shown) may be connected tothe tube 98 to regulate the flow of air into and out of the bladder 96.

FIG. 12 illustrates another embodiment of a prosthetic foot 10 similarto that shown in FIG. 11A, except that in FIG. 12 there are provided twoankle plates 14 and 15 layered on top of one another in slidingarrangement. The top plate 14 is preferably monolithically formed from ahigh strength composite material with a curvilinear ankle section 36 andan upper attachment area 34, such as described above. The bottom plate15 is also preferably monolithically formed with a curvilinear anklesection 37 and an upper attachment area 35. The upper attachment areas34 and 35 are preferably attached to pylon member 32 through couplingdevice 42, with bolts or screws (not shown) extending through the upperattachment areas 34 and 35 and coupling device 42 into the pylon member32.

The lower plate 15 preferably extends forward past the front of ankleplate 14, and more preferably the plate 15 extends to the front of theankle block 16. Strap 23 a secures the plates 14 and 15, the ankle block16 and the foot plate 12 at the rear of the ankle block. Strap 23 bsecures the plates 14 and 15 at the front of the plate 14. By providingan upper and lower plate 14 and 15, respectively, these plates arecapable of bending and sliding relative to each other. Thisadvantageously reduces the bending resistance of the prosthesis whilemaintaining adequate vertical support strength.

FIGS. 13 and 14 illustrate another alternative embodiment for aprosthetic foot 10 similar to the embodiment shown in FIG. 10 above.Thus, the foot 10 generally comprises a lower foot plate 12, an upper,smaller ankle plate 14, and a plurality of inflatable bladders disposedbetween the foot plate 12 and the ankle plate 14. More preferably, arear or heel bladder 19 a is provided near the rear of the ankle plate14, and a pair of toe bladders 19 b which are in fluid communicationwith each other are provided at the front of the ankle plate (see FIG.14). A strap 23 is provided at the rear of the ankle plate 14surrounding the bladder 19 a and foot plate 12. Optionally, plates 29 a,29 b, 29 c and 29 d may be provided between each of the bladders and theankle plate 14 and/or foot plate 12.

The pressure in the heel bladder 19 a is controlled by valve 21 a, whilepressure in the toe bladders 19 b is controlled by valve 21 b. It willbe appreciated that although FIG. 13 shows one valve 21 b controllingthe pressure in both toe bladders 19 b, it is also contemplated thateach toe bladder 19 b may be controlled by separate valves. The valves21 a and 21 b may be operatively connected to the bladder via tubing orother suitable communication passages. In the embodiment shown in FIG.13, tubings 17 a and 17 b connect the heel bladder 19 a and toe bladders19 b, respectively, to the appropriate valves. Beyond the valves 21 aand 21 b, the tubings 17 a and 17 b are preferably joined, with a singletubing 17 c extending away therefrom to a gas or air input/output source21 d. A valve 21 c controls the pressure through the tubing 17 c.

It will be appreciated that the valve control system described withrespect to FIGS. 13 and 14 may be used with other types of inflatablebladders. For instance, valves such as FIGS. 13 and 14 may be used toinflate a stiffener 52 such as illustrated in FIG. 11D above.Furthermore, separate tubings may be used to adjust pressure in multiplestiffeners provided in an ankle block as described with respect to FIG.11A.

FIGS. 15A–16A illustrate another embodiment of a prosthetic foot 10incorporating an air pump system for actively or passively controllingpressure within inflatable bladders. The components of this system areshown in FIG. 15A. A syringe type air pump 90 is provided with an airintake port 92 having a check valve. The syringe pump 90 is connected bya tube 88 to an accumulator 86. The accumulator 86 is connected by atube 85 to an electronic control system 84 including a valve manifold.Also connected to the control system 84 are an air vent 87, and tubes 83a and 83 b providing fluid communication to inflatable bladders 19 a and19 b, respectively.

These components are collectively arranged into a prosthetic foot 10,shown in FIG. 16A. It will be appreciated that the arrangement ofcomponents in FIG. 16A is purely exemplifying and thus otherarrangements are possible as well. As described in other embodimentsabove, the inflatable bladders 19 a and 19 b are provided between ankleplate 14 and foot plate 12. Connected to the upper attachment area 34 ofthe prosthetic foot 10 are a pair of schematically shown telescopingpylons 95 and 97. Further details regarding telescoping and other typesof pylons that may be used in conjunction with the embodiments of thepresent invention are described below and in applicant's copendingapplication entitled SHOCK MODULE PROSTHESIS, Ser. No. 09/289,533, filedApr. 19, 1999, and U.S. Pat. No. 5,458,656, the entirety of each ofwhich are hereby incorporated by reference. Lower pylon 95telescopically engages upper pylon 97, such that pylons 95 and 97 arepreferably slidingly and rotationally interengaged with each other.Preferably, a resilient element, such as a coil compression spring, isproximally fixed within upper pylon 97 and distally fixed within lowerpylon 95. Thus, when a force is applied to the prosthetic foot, thepylons 95 and 97 move toward one another in a compressed configuration.When the force is released, the pylons move apart to a restconfiguration.

The syringe 90 preferably includes a plunger 91 and a cylinder 93.Plunger 91 is attached to the upper pylon 95, such as with bracket 99 orother means. Cylinder 93 is preferably similarly attached to the lowerpylon 97. Control system 84 and accumulator 86 are also preferablyattached to lower pylon 97. Accordingly, when force is applied to theprosthetic foot 10, the relative movement of the pylons causes theplunger 91 to move in and out of the cylinder 93 and produce airpressure through the tube 88. Air is preferably drawn through a filterelement comprising air intake port 92 (not shown in FIG. 16A). The fluidis stored in accumulator 86 and passed on to the valve manifold of theelectronic control system 84. The manifold preferably electronicallycontrols how much air is provided to each of the inflatable bladders 19a and 19 b, and also how much air will be vented out through tube 87.Thus, the pump system of FIGS. 15A–16 uses pressure built up by theamputee's own motion and determines an appropriate pressure to beprovided to each of the inflatable bladders.

For example, FIG. 15B illustrates schematically one embodiment for thevalve manifold of the control system 84. When the bladders 19 a and 19 brequire more air for additional support, the control system 84 opensvalves 103, 105 and 107 to allow air to pass from the accumulator 86 tothe bladders 19 a and 19 b through tubes 83 a and 83 b. When it isdesired to deflate bladders 19 a and 19 b, the valve 101 can be openedand valve 103 can be closed so that air passes from the bladders 19 a,19 b through tubes 83 a and 83 b and out tube 87. In addition, when oneof the bladders requires more or less air than the other, valves 105 and107 can be selectively adjusted to individually inflate or deflatebladder 19 a or 19 b, with either valve 101 or valve 103 remaining open.The valves can be sensed and controlled electronically or via acomputer. It will be appreciated that a variety of valve configurationsmay be employed to selectively adjust the appropriate pressure for thebladders 19 a and 19 b.

It will further be appreciated that although FIG. 16A depicts thesyringe as being attached externally to the pylons, the syringe may alsobe attached internally to the pylons. Furthermore, other components ofthe pump system, such as the accumulator and the valve manifold, mayalso be provided within the pylons. One such embodiment is described byFIG. 23, below.

FIG. 16B illustrates another prosthetic foot incorporating an inflatablebladder 19 and a CO2 cartridge for adjusting the pressure within thebladder. The embodiment of FIG. 16B is similar to the prosthetic foot ofFIG. 9, and includes an inflatable bladder 19 sandwiched between anupper ankle plate 14 and a lower foot plate 12. A pylon 32 is attachedto the ankle plate 14 through a vertically oriented upper attachmentmember 34 and a curvilinear ankle section 36, all of which arepreferably monolithically formed. A CO2 cartridge 132 is preferablyattached to the exterior surface of the pylon 32, and is connected tothe bladder 19 through a fluid line 134 having a valve 21. The valve 21in one embodiment is electrically controlled, with a pressure sensor tocontrol the amount of CO2 delivered to the bladder.

FIG. 17 shows another embodiment of a prosthetic foot 10. Thisembodiment is similar to that shown in FIG. 12 above in that itgenerally comprises two ankle plates 14 and 15, an ankle block 16 and afoot plate 12. However, in the prosthetic foot 10 of FIG. 17, the plates14 and 15 both extend to the front of the ankle block 16. Furthermore,the ankle plate 16 is more preferably a chambered urethane having aplurality of openings extending therethrough. Specifically, in additionto the cylindrical slots 50 and 51, the ankle block 16 of FIG. 17 alsohas an opening 55 that is substantially oblong when viewed from the sideand that extends across the transverse dimension of the ankle block 16.Similar to the embodiments described above, the opening 55 can be filledwith other materials for adjusting the stiffness of the block. Openingscan be enclosed, if desired, defining closed chambers filled with acompressible fluid such as air.

FIG. 18 shows a similar embodiment to that of FIG. 17, except that theankle block 16, in addition to the cylindrical slots 50 and 51, hasthree additional openings 55 a, 55 b and 55 c. More preferably, slots 55a and 55 c are cylindrical similar to slots 50 and 51, while slot 55 bhas a substantially dual concave-out shape when viewed from the side.All five of these openings can remain empty or may be filled withstiffeners and/or fluid as described above. It will be appreciated thatthe number and shapes of these openings may be varied giving dueconsideration to the goals of the desired prosthetic foot. None, some orall of the openings filled may be filled with stiffeners, in order toobtain desired performance characteristics for the foot 10.

FIG. 19 illustrates another embodiment of a prosthetic foot 10. Like theembodiments described above, this foot includes two ankle plates 14 and15, an ankle block 16 and a foot plate 12. The ankle block 16 alsoincludes cylindrical slots 50 and 51 similar to those described above.Within the slots 50 and 51 are inserted cams 112 and 114 that rotateabout shafts 113 and 115, respectively. These rotatable cams, wheninserted, cause the shape of the slots to deform elliptically incompliance with the shape of the cams. This in turn adjusts thecompliance of the ankle block depending on the orientation of each ofthe cams. Thus, as shown in FIG. 19, one cam may be oriented such thatits cross-section is aligned substantially transversely relative to aforward walking motion, while the other cam may be oriented such thatits cross-section is aligned substantially parallel to a forward walkingmotion. These cams may be rotated while within the ankle block 16 todifferent orientations as well.

The cams are preferably made from a material stiffer than that of theankle block 16, and more preferably, made be made of metal or othermaterials. Thus, inserting a cam into the ankle block 16 increases thestiffness of that part of the ankle block. Moreover, as shown in FIG.19, when one cam 112 is oriented substantially transversely to a forwardwalking motion, and another cam 114 is oriented substantially parallelto a forward walking motion, the transverse cam 112 preferably impartsgreater stiffness to that part of the ankle block than does the othercam 114. Furthermore, because the cams are rotatable, the stiffness ineach portion of the ankle block is adjustable. It will also beappreciated that although FIG. 19 shows only two cams, fewer or greaternumber of rotatable cams can also be incorporated into the ankle block.

FIG. 19 also illustrates a strap 110 attached to the rear face of upperattachment area 35 of ankle plate 15. This strap 110 preferably extendsdown and is attached to the foot plate 12. The strap 110 advantageouslyis provided to adjust the relative flexing properties between the ankleplates and the foot plate and to control the maximum distance betweenthe respective plates. It will be appreciated that the strap shown inFIG. 19 may be incorporated in any of the embodiments above in which anankle support member is provided between an ankle plate and a footplate.

FIG. 20 illustrates another embodiment of a prosthetic foot 10. In thisembodiment, the ankle block 16 includes a front chamber 119 and a rearchamber 121, each containing a stiffener 118 and 120, respectively,arranged transversely therein relative to a forward walking motion. Thechambers 119 and 121 are sized to allow the stiffeners 118 and 120 tomove forward and backward relative to a forward walking motion withineach of the chambers. Thus, as shown in FIG. 20, when the stiffeners aregenerally circular when viewed from the side, each of the chambers hasan oblong shape. By being able to move the stiffeners 118 and 120 withinthe ankle block 16, a user can selectively adjust the stiffness of theprosthetic foot by changing the position of the stiffeners.

In the embodiment shown in FIG. 20, the stiffeners 118 and 120 arecylindrical rods which are attached to arms 122 and 124, respectively.These arms are joined in a middle chamber 117 by an actuator 116,schematically shown in FIG. 20. In one embodiment, the actuator 116 is amotor that preferably adjusts the location of the stiffeners 118, 120 inthe chambers 119, 121 to provide desired stiffness in a particularlocation of the ankle block 16. The motor 116 may, for example, be amanual or servo motor. In one embodiment, the arms 122 and 124 areintegrally formed such that a constant distance is maintained betweenthe front stiffener 118 and the rear stiffener 120. The motor 116 thenadjusts the position of the arms such that the stiffeners are in thesame relative position within each of their respective chambers.

It will be appreciated that other embodiments are also possible. Forinstance, the stiffeners need not be separated by a constant distance,and can be adjustable to shorten or lengthen the distance therebetween.This may be accomplished, for example, by providing the actuator 116 asa knob that can be turned in one direction to shorten the distancebetween the stiffeners and in the other direction to lengthen thedistance between the stiffeners. In such an embodiment, the arms 122 and124 may be opposingly threadingly engaged with the actuator 116.Furthermore, it will be appreciated that where the actuator 116 is aknob, the stiffeners can be separated by a constant distance withintegrally formed arms 122 and 124, with the knob capable of beingturned to adjust the location of the stiffeners within their respectivechambers while maintaining a constant distance therebetween.

FIG. 21 illustrates another embodiment of a prosthetic foot 10. Similarto the embodiments above, this prosthetic foot 10 includes an ankleblock 16 disposed between ankle plates 14 and 15 and foot plate 12. Theankle block 16 preferably includes a single cylindrical slot 50 in thefore portion of the block, the slot 50 including a stiffener 52 therein.It will be appreciated, however, that additional slots may be providedin the ankle block 16 as described above.

As shown in FIG. 21, the ankle block 16 preferably includes in the rearportion a wedge cut-out 125 adjacent to and extending to the foot plate12. The cut-out 125 is preferably disposed directly below the pylon 32to correspond substantially to the location of a human heel. Morepreferably, a wedge piece 126 is inserted into the cut-out 125 of theankle block 16 to provide additional support in the heel portion of theprosthetic foot 10. In one embodiment, as shown in FIG. 21, the wedgepiece 126 has a rear surface that is substantially flush with the rearsurface of the ankle block and has a convex shape that mates with thewedge cut-out 125. The wedge piece is preferably fabricated fromurethane rubber, although other materials may be used as well. Becausethe wedge piece 126 is removable from the ankle block 16, wedge piecesof varying stiffness may be inserted into the wedge cut-out to providedesired degrees of stiffness in the heel. For example, a wedge piecethat has a stiffness that is greater or less than that of the ankleblock may be inserted into the wedge cut-out. It will also beappreciated that using wedge pieces of different sizes and shapes mayalso provide desired compliance characteristics. Thus, the prosthesismay be used without a wedge piece 126, or with a wedge piece of varyingsize or stiffness to adjust the performance characteristics of theprosthesis.

FIG. 21 also illustrates a strap 110 incorporated with an adjustmentmechanism connected to the pylon 32. A housing 128 for the strap isprovided on the rear surface of the upper attachment area 35, thehousing having a slot 129 extending vertically therethrough. The strap110 is preferably able to move through the slot 129 in order to tightenor loosen the connection with the foot plate 12, as indicated by thearrows shown in the figure. Within the slot 129 the strap can be heldand locked in place by any appropriate means, such as a press-fit,screws, pins, brackets, etc. FIG. 22 further illustrates that an insert,such as a C-shaped insert 130, can be placed within adjacent andconnecting portions of the strap 110 to further adjust the tension inthe strap.

In another embodiment, a syringe-type air pump system similar to thatshown in FIGS. 15A–16 is produced by the action of the telescopingpylons as shown in FIG. 23. In such an embodiment, an inner pylon 214acts as the plunger of the syringe, and an outer pylon 212 acts as thecylinder of the syringe. As the inner pylon 214 is compressed anddecompressed toward and away from the outer pylon 212 with a spring 220or other compression member, fluid pressure is generated within achamber defined between the two pylons. When the inner pylon 214 is theupper of the two pylons, the inner pylon is preferably sealed at the topof the chamber, and the outer pylon is preferably sealed at the bottomof the chamber. More preferably, the sealing of the chamber may beprovided using valves 224, 248 to regulate fluid flow into and out ofthe chamber. A valve 248 provided at the bottom of the chamber in theouter pylon preferably leads to a fluid reservoir 250, which may beprovided within the outer pylon or separately therefrom. As with theaccumulator above, the reservoir 250 may be connected via a fluid line236 to an inflatable bladder 206 that supports a prosthetic foot.

More particularly, FIG. 23 illustrates a prosthetic foot 200 having aninflatable bladder similar to that shown in FIG. 9. Similar to theprosthetic foot described above, the prosthetic foot 200 generallycomprises a lower foot plate 202, an upper, smaller ankle plate 204, andan inflatable bladder 206 disposed between the foot plate 212 and theankle plate 214. The bladder 206 is preferably secured to the platesthrough straps 208, or by other means as described above.

The pressure in the bladder 206 is controlled through connection to anactive shock module 210. Shock module 210 includes outer pylon 212 andinner pylon 214, shaped and adapted for smooth relative motion. Pylons212 and 214 are preferably slidingly and rotationally interengaged witheach other while retaining their operative horizontal alignment witheach other through a relatively close fit between the inside dimensionsof outer pylon 212 and the outside dimensions of inner pylon 214. Theinner pylon 214 has an enlarged outside diameter at its proximal end,approximately equal to the outside diameter of the outer pylon 212. Thisenlarged diameter portion of the inner pylon 214 therefore extendsbeyond the proximal end of the outer pylon 212 and does not extend intothe outer pylon 212.

Pylon 214 also has a female pyramid fitting 216 at its proximal end, forattachment to a stump socket (not shown). Outer pylon 212 preferably hasa cylindrical outer surface to facilitate the attachment of varioustypes of prosthetic feet using conventional prosthetic couplers. Forexample, the lower end of pylon 212 may be attached to prosthetic foot200 via a pyramid coupler 218 and female pyramid fitting 220. The femalecoupler 218 is slipped over the lower extremity of the outer pylon 212and clamped into position.

Shock module 210 preferably includes a hybrid spring-fluid resilientelement, comprising an internal coil compression spring 220 incombination with a compressible fluid such as air. Spring 220 ispreferably proximally fixed with respect to inner pylon 214 and distallyfixed with respect to outer pylon 212 via spring support 222.Optionally, a valve 224 is provided within pylon 214 to vary thepressure of the fluid inside of shock module 210. A torque-resistingcuff 226 provides torsion-resistance to the prosthesis and also keepsdirt and other debris from getting between pylons 212 and 214 andaffecting their relative motion. Further details on shock modules thatmay be used in conjunction with the embodiments of the present inventionmay be found in U.S. application Ser. No. 09/556,249, entitled ACTIVESHOCK MODULE PROSTHESIS, filed Apr. 24, 2000, the entirety of which ishereby incorporated by reference.

An end cap 228 is preferably provided below the spring support 222within the outer pylon 212. Both the end cap 228 and the spring support222 are preferably threaded to engage an internally threaded surface 230of the outer pylon 212. Both the spring support 222 and the end cap 228preferably have an internal hole 232, 234, respectively, which allowsthe compressible fluid to pass therethrough to a fluid reservoir 250,described below. A cover cap 238 preferably seals the hole 232, 234below the end cap 228. This cover cap is preferably threadingly engagedwith a second internally threaded surface 240 of the outer pylon 212,the second internally threaded surface 240 having a larger diameter thanthat of the first internally threaded surface 230. Along the surfacethat secures end cap 228, the cover cap 238 is provided with an O-ringnotch 242 that abuts against the horizontal surface 244 between thesurfaces 230 and 240. By providing an O-ring 246 into this notch, whenthe cover cap is screwed into the internally threaded surface 240against the horizontal surface 244, the O-ring 246 is compressed toprovide a seal with respect to the interior of pylon 212.

The cover cap 238 preferably includes a valve 248 to control the passageof fluid from inside the inner pylon to a reservoir 250 contained withinthe outer pylon. This reservoir is defined on its sides by theinternally threaded surface 240, at one end by the cover cap 238, and atits other end by a reservoir cap 252 which is also threadingly engagedin the surface 240. Below the threaded surface 240 the bottom of theouter pylon 212 on its inside surface 254 is preferably nonthreaded, andthe reservoir cap 252 has a larger diameter portion at its bottom thatabuts against the horizontal surface 256 between surfaces 240 and 254.An O-ring notch 258 is provided in the reservoir cap, and O-ring 260 isinserted into the notch which compresses against horizontal surface 256to form a fluid tight seal.

The torque-resisting cuff 226 is preferably configured to oscillatebetween a relatively straight vertical position, when the outer pylonand inner pylon are moved relatively far apart, and a curved position,when the outer pylon and inner pylon are compressed relative to oneanother. FIG. 23 illustrates the shock module 210 in a fully compressedconfiguration such that the cuff 226 is curved and the inner pylon 214extends as far as possible into the outer pylon 212. More particularly,when fully compressed the enlarged outer diameter portion of the innerpylon 214 preferably abuts against the proximal end of the outer pylon212.

Similar to the syringe system described with respect to FIGS. 15A–16Aabove, the telescoping pylons of the active shock module 210 generatepressure within the bladder 206 by the amputee's motion causing thepylons to move toward and away from each other. More particularly, therelative motion of the pylons, in conjunction with the compressiblefluid and/or spring or other compressible medium inside the pylons,causes fluid pressure to build up within the inner pylon. Pressure mayalso be regulated within the inner pylon through the valve 224. Valve248 at the bottom of the inner pylon regulates fluid pressure and can beopened to transfer fluid into the reservoir 250. Fluid line 236preferably connects the reservoir to the bladder 206, and valve 264controls the flow of fluid into the bladder in order to adjust thepressure inside the bladder. It will further be appreciated thatpressure step-up or amplification may be provided by changing therelative sizing of the telescoping pylons.

It will be appreciated that although the active shock module has beendescribed with respect to inflatable bladder 206, the shock module mayalso be used with other inflatable members, such as the stiffener ofFIG. 11D. Furthermore, an active shock module may be used to inflatemultiple members, such as shown in FIGS. 10, 13, and 14.

Although this invention has been disclosed in the context of certainpreferred embodiments and examples, it will be understood by thoseskilled in the art that the present invention extends beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the invention and obvious modifications and equivalentsthereof. Thus, it is intended that the scope of the present inventionherein disclosed should not be limited by the particular disclosedembodiments described above, but should be determined only by a fairreading of the claims that follow.

1. A prosthetic foot comprising: a forefoot portion, a heel portion andan intermediate region between the forefoot portion and the heelportion; an ankle plate provided at least partially above, and separatedfrom, the forefoot portion, the heel portion and the intermediateregion; an anterior ankle block made of resilient material connectingthe forefoot portion to the ankle plate; and a posterior ankle blockmade of resilient material connecting the heel portion to the ankleplate.
 2. The prosthetic foot of claim 1, wherein the ankle blocks forma unitary ankle block that separates the ankle plate from the forefootportion, the heel portion and the intermediate region.
 3. The prostheticfoot of claim 1, wherein said ankle blocks comprise a compressiblematerial.
 4. The prosthetic foot of claim 1, wherein said ankle blockscomprise polyurethane.
 5. The prosthetic foot of claim 1, wherein saidankle blocks comprise a foam material.
 6. The prosthetic foot of claim1, wherein at least one portion of said ankle blocks is made of amaterial having a density between about 150 and 1500 kg/m³.
 7. Theprosthetic foot of claim 1, wherein said ankle blocks providesubstantially the sole means of support between said forefoot and heelportions and said ankle plate.
 8. The prosthetic foot of claim 7,wherein said ankle blocks are disposed substantially entirely betweensaid forefoot and heel portions and said ankle plate.
 9. The prostheticfoot of claim 1, wherein the forefoot portion and the heel portion areintegrally formed.
 10. The prosthetic foot of claim 1, wherein the ankleplate includes a curvilinear ankle section and an upper attachmentsection.
 11. A prosthetic foot comprising: a forefoot portion and a heelportion; an ankle plate provided at least partially above the forefootportion and the heel portion; an anterior ankle block made of resilientmaterial connecting the forefoot portion to the ankle plate; and aposterior ankle block made of resilient material connecting the heelportion to the ankle plate; wherein the anterior ankle block andposterior ankle block provide substantially the sole means of connectionbetween the ankle plate and the forefoot and heel portions.
 12. Theprosthetic foot of claim 11, wherein the ankle blocks form a unitaryankle block that separates the ankle plate from the forefoot portion andthe heel portion.
 13. The prosthetic foot of claim 11, wherein saidankle blocks comprise a compressible material.
 14. The prosthetic footof claim 11, wherein said ankle blocks comprise polyurethane.
 15. Theprosthetic foot of claim 11, wherein at least one portion of said ankleblocks is made of a material having a density between about 150 and 1500kg/m³.
 16. The prosthetic foot of claim 11, wherein said ankle blocksare disposed substantially entirely between said forefoot and heelportions and said ankle plate.
 17. The prosthetic foot of claim 11,wherein the forefoot portion and the heel portion are integrally formed.18. The prosthetic foot of claim 11, wherein the ankle plate includes acurvilinear ankle section and an upper attachment section.